Symmetrical hydroxydiaryl sulfoxides are known and can be prepared by the following reaction. ##STR1## These compounds are then oxidized to the corresponding sulfoxides. The unsymmetrical hydroxydiaryl sulfoxides are not prepared by this reaction, but normally require four or more low yield consecutive reactions. Some of the symmetrical hydroxydiaryl compounds such as 4,4'thiobis(resorcinol) have been used to stabilize pine rosin.